It is often difficult for a new signing to make a big impact straight away, but some clubs have been lucky enough to sign catalysts for championships.
We’ve taken a look back at nine of the most important signings ahead of title-winning campaigns.
Looking back, Van Persie and Manchester United were a match made in heaven. Sir Alex Ferguson was determined to wrestle back the title from noisy neighbours Manchester City, and Van Persie was desperate for trophies after he ended his last seven years at Arsenal empty-handed.
City were hopeful of signing Van Persie themselves, but Fergie ensured otherwise and the results were glorious. Thirty goals in all competitions in his debut season saw United win the Premier League.
Ferguson went on to compare the striker’s impact to that of Eric Cantona, describing his wonderful volley against Aston Villa – which fittingly saw United clinch the title – as “the goal of the century”.
— Manchester United (@ManUtd) May 2, 2016
United’s signing of Van Persie came as a direct response to Aguero’s exploits for Manchester City in the previous season.
Aguero was one of City’s statement signings in the summer of 2011 and went on to score 30 goals in all competitions in his debut season for the club.
It took the striker only nine minutes after coming on as a substitute for his debut to open his account for the club, and we really don’t need to tell you how that campaign ended.
Perhaps the most obvious example which springs to mind. A lack of goals had seen Manchester United pipped to the last ever First Division title by Leeds United in 1992.
Cantona had played a cameo role in helping Leeds become champions, and shocked the football world by moving across the Penines to joined the Whites’ arch rivals only months later.
“If ever there was one player, anywhere in the world, that was made for Manchester United, it was Cantona,” Ferguson wrote in his autobiography, Managing My Life.
“He swaggered in, stuck his chest out, raised his head and surveyed everything as though he were asking: ‘I’m Cantona, how big are you? Are you big enough for me?’ ”
Cantona was not only the catalyst for the Red Devils winning their first title for 26 years in 1992-93, but for the following two decades of success which followed.
The man it’s impossible not to love, Kante actually qualifies for this list twice.
Leicester City supporters were still ruing the departure of Esteban Cambiasso when Kante arrived at the King Power in a £5.6million deal from Caen.
The midfield dynamo more than filled the boots of Cambiasso as he took the Premier League by storm in Leicester’s shock title win.
Those performances led to big-money move to Chelsea, and Kante shone once more as Chelsea went from finishing tenth to first, with the France international named PFA Player of the Year and FWA Footballer of the Year.
Remember when Claudio Bravo was Manchester City’s No.1 goalkeeper? Bit awkward, wasn’t it, like farting at a funeral.
But then the following season Ederson came in, younger, more expensive, less experienced. When it looked like City needed a steady, calming influence to look after organise their defence, they signed a 23-year-old who would often play in midfield for Benfica’s youth teams.
City ended the season having conceded the fewest goals and scored the most, with Ederson pivotal in both.
“It’s like having Ronald Koeman in goal,” Sean Dyche gushed.
Alan Shearer enjoyed his first 30+ goal season in 1993-94, but if Blackburn were to overhaul the eight point buffer with which Manchester United won the league that season, the England striker needed some help.
Mike Newell (six goals) and Kevin Gallacher (seven goals) were Shearer’s supporting strikers, so they decided to splash £5million on Sutton, fresh off the back of 25 league goals for Norwich City.
Sutton and Shearer instantly clicked, and the SAS bagged 49 goals between them as Blackburn went on to win the title.
A very scary man, Stam’s impact on Manchester United was equally frightening.
Arsenal had won the Double in 1997-98, with an ageing Gary Pallister playing his final season at the heart of United’s defence.
Pallister left for Middlesbrough in the summer and Stam arrived in a £10.75million move from PSV.
The Red Devils went on to piss on Arsenal’s bonfire by winning the Treble, with Stam making 51 appearances in all competitions.
It takes a brave man to move from Tottenham to Arsenal, it takes an even braver man to do so six months after committing his future to the White Hart Lane club.
It takes an ever braver man to then go and win the Double with their North London rivals.
Fair play, Sol.
Jose Mourinho’s first season back at Chelsea was somewhat underwhelming as the Blues failed to win a trophy.
With Frank Lampard leaving the club in the summer, Mourinho need a new talisman in midfield and swooped to sign Fabregas from Barcelona.
Arsenal chose not to use their option to re-sign the midfielder, who went on to add the creativity and guile to Chelsea’s ranks.
The Blues won the league at a canter, thanks in no small part to Fabregas’ 18 assists.